Oncotarget

Research Papers:

Identification of Kinase Inhibitors that Target Transcription Initiation by RNA Polymerase II

José M. Morachis, Ruo Huang and Beverly M. Emerson _

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Oncotarget. 2011; 2:18-28. https://doi.org/10.18632/oncotarget.212

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Abstract

José M. Morachis1,2, Ruo Huang1, Beverly M. Emerson1

1Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, USA

2Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, USA

Keywords: RNA polymerase II, transcription therapy, core promoters, kinase inhibitors, p53, p21, Fas/APO1

Received: January 21, 2011; Accepted: January 25, 2010; Published: January 27, 2010;

Correspondence:

Beverly M. Emerson, e-mail:

Abstract

Our current understanding of eukaryotic transcription has greatly benefited from use of small molecule inhibitors that have delineated multiple regulatory steps in site-specific initiation and elongation of RNA synthesis by multiple forms of RNA polymerase (RNAP). This class of "transcription" drugs is also of therapeutic interest and under evaluation in clinical trials. However, to date very few small molecules that directly abolish transcription have been identified, particularly those that act at the level of RNAP II initiation. Using a biochemical assay that measures transcription from recombinant, natural p53-responsive promoters and an artificial "super" promoter, we have identified three distinct small molecules that inhibit mRNA synthesis in vitro. Unexpectedly, these are kinase inhibitors, Hypericin, Rottlerin, and SP600125, with known substrates, which we find also strongly impair transcriptional initiation (IC50s = µM range) by targeting specific components of the RNAP II pre-initiation complex. When measured before and during transcription in vitro, one common target of inhibition by all three compounds is modification of the TATA Binding Protein (TBP) within the RNAP II holocomplex as it converts to an active transcribing enzyme. On this basis, by blocking the critical step of TBP modification, transcriptional initiation is effectively abolished even on structurally distinct core promoters.


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